Stereoscopic images of a scene are produced by viewing two (or more) images with different perspectives of a scene in a stereo image pair. One image in the stereo image pair is viewed with one eye and the other image in the stereo image pair is viewed with the other eye. The viewing of the two images can be done simultaneously or in an alternating fashion provided the alternating images are presented fast enough that the image changes are not perceptible to the viewer. It is the differences in perspectives between the two (or more) images in the stereo image pair that provide a perception of depth to the viewer. To provide different perspectives in stereo image pairs, typically pairs of images are captured simultaneously with an image capture device that has two (or more) image capture devices that are separated by a distance to provide different perspectives of the scene. A single stereo image pair can be used to provide a still stereoscopic image of a scene. A series of sequential stereo image pairs can be used to provide a stereoscopic video of a scene. Typically the two images in a stereo image pair include a left image and a right image where the left image has a perspective as seen by the viewer's left eye and the right image has a perspective as seen by the viewer's right eye.
Methods for viewing stereoscopic images are well known in the art. Methods include head mounted displays where the left and right images in a stereo image pair are presented to the left and right eyes of the viewer. Another method includes a display that alternately presents a right image and a left image and the viewer wears shutter glasses that are synchronously operated with the display such that the right eye of the viewer is permitted to see the display only when the right image is presented and the left eye of the viewer is permitted to see the display only when the left image is presented. Yet another method includes a display that alternately presents a right image and a left image to the viewer wherein the polarization of the right image is different from the left image and the viewer wears polarized glasses such that the viewer's right eye can only see the right image and the viewer's left eye can only see the left image. A further method of viewing stereoscopic images is provided by a display that divides the images in a stereo image pair into vertical segments with optical limiters such that the right eye of the viewer can only see the divided vertical segments of the right image and the left eye of the viewer can only see the divided vertical segments of the left image. In all these methods for viewing stereoscopic images, it is difficult for multiple viewers to simultaneously view both stereoscopic images and non-stereoscopic images. In addition, viewers do not find it comfortable to wear glasses for all types of image viewing.
Monocular devices for presenting an image to one eye of a viewer are also well known in the art. U.S. Pat. No. 6,452,572 describes several different types of monocular head mounted display devices where the monocular display can be adjusted to suit the preferences of the viewer and the monocular device can be moved in and out of the viewer's field of view. U.S. Pat. No. 6,680,802 discloses a monocular head mounted display device which utilizes a see-thru prism to allow images to be presented to the viewer while the viewer can simultaneously view the surrounding environment. U.S. Pat. No. 6,771,424 discloses a head mounted display for one eye with a holder that contacts the sides and front of the head. However, methods for viewing stereo image pairs using a monocular device are not described.
Therefore, a need persists for providing multiple viewers the option to simultaneously view either a non-stereoscopic image or a stereoscopic image.